
var isIE = (document.all) ? true : false;
//获取dom id
var $ = function(id) {
	return "string" == typeof id ? document.getElementById(id) : id;
};
//创建类
var Class = {
		create: function() {
			return function() {
				this.initialize.apply(this, arguments);
			}
		}
	}
	//继承
var Extend = function(destination, source) {
		for (var property in source) {
			destination[property] = source[property];
		}
	}
	//绑定事件
var Bind = function(object, fun) {
	return function() {
		return fun.apply(object, arguments);
	}
}
var BindAsEventListener = function(object, fun) {
		return function(event) {
			return fun.call(object, (event || window.event));
		}
	}
	//获取样式
var CurrentStyle = function(element) {
		return element.currentStyle || document.defaultView.getComputedStyle(element, null);
	}
	// Demo by /
	//添加事件方法
function addEventHandler(oTarget, sEventType, fnHandler) {
	if (oTarget.addEventListener) {
		oTarget.addEventListener(sEventType, fnHandler, false);
	} else if (oTarget.attachEvent) {
		oTarget.attachEvent("on" + sEventType, fnHandler);
	} else {
		oTarget["on" + sEventType] = fnHandler;
	}
};
//移除事件
function removeEventHandler(oTarget, sEventType, fnHandler) {
	if (oTarget.removeEventListener) {
		oTarget.removeEventListener(sEventType, fnHandler, false);
	} else if (oTarget.detachEvent) {
		oTarget.detachEvent("on" + sEventType, fnHandler);
	} else {
		oTarget["on" + sEventType] = null;
	}
};
//拖放程序
var Drag = Class.create();
Drag.prototype = {
	//拖放对象
	initialize: function(drag, options) {
		
		this.Drag = $(drag); //拖放对象
		
		this._x = this._y = 0; //记录鼠标相对拖放对象的位置
		this._marginLeft = this._marginTop = 0; //记录margin
		//事件对象(用于绑定移除事件)
		this._fM = BindAsEventListener(this, this.Move);
		this._fS = Bind(this, this.Stop);
		this.SetOptions(options);
		//对区域进行控制
		this.Limit = !!this.options.Limit;
		this.mxLeft = parseInt(this.options.mxLeft);
		this.mxRight = parseInt(this.options.mxRight);
		this.mxTop = parseInt(this.options.mxTop);
		this.mxBottom = parseInt(this.options.mxBottom);
		this.LockX = !!this.options.LockX;
		this.LockY = !!this.options.LockY;
		this.Lock = !!this.options.Lock;
		this.onStart = this.options.onStart;
		this.onMove = this.options.onMove;
		this.onStop = this.options.onStop;
		this._Handle = $(this.options.Handle) || this.Drag;
		this._mxContainer = $(this.options.mxContainer) || null;
		this.Drag.style.position = "absolute";
		//透明
		if (isIE && !!this.options.Transparent) {
			//填充拖放对象
			//with(this._Handle.appendChild(document.createElement("div")).style) {
				this._Handle.appendChild(document.createElement("div")).style.width='100%';
				this._Handle.appendChild(document.createElement("div")).style.height='100%';
				this._Handle.appendChild(document.createElement("div")).style.backgroundColor="#fff";
				this._Handle.appendChild(document.createElement("div")).style.filter="alpha(opacity:0)";
				this._Handle.appendChild(document.createElement("div")).style.fontsize=0;
//				
//				width = height = "100%";
//				backgroundColor = "#fff";
//				filter = "alpha(opacity:0)";
//				fontSize = 0;
//			}
		}
		//修正范围
		this.Repair();
		addEventHandler(this._Handle, "mousedown", BindAsEventListener(this, this.Start));
	},
	//设置默认属性
	SetOptions: function(options) {
		this.options = { //默认值
			Handle: "", //设置触发对象（不设置则使用拖放对象）
			Limit: false, //是否设置范围限制(为true时下面参数有用,可以是负数)
			mxLeft: 0, //左边限制
			mxRight: 9999, //右边限制
			mxTop: 0, //上边限制
			mxBottom: 9999, //下边限制
			mxContainer: "", //指定限制在容器内
			LockX: false, //是否锁定水平方向拖放
			LockY: false, //是否锁定垂直方向拖放
			Lock: false, //是否锁定
			Transparent: false, //是否透明
			onStart: function() {}, //开始移动时执行
			onMove: function() {}, //移动时执行
			onStop: function() {} //结束移动时执行
		};
		Extend(this.options, options || {});
	},
	//准备拖动
	Start: function(oEvent) {
		if (this.Lock) {
			return;
		}
		this.Repair();
		//记录鼠标相对拖放对象的位置
		this._x = oEvent.clientX - this.Drag.offsetLeft;
		this._y = oEvent.clientY - this.Drag.offsetTop;
		//记录margin
		this._marginLeft = parseInt(CurrentStyle(this.Drag).marginLeft) || 0;
		this._marginTop = parseInt(CurrentStyle(this.Drag).marginTop) || 0;
		//mousemove时移动 mouseup时停止
		addEventHandler(document, "mousemove", this._fM);
		addEventHandler(document, "mouseup", this._fS);
		if (isIE) {
			//焦点丢失
			addEventHandler(this._Handle, "losecapture", this._fS);
			//设置鼠标捕获
			this._Handle.setCapture();
		} else {
			//焦点丢失
			addEventHandler(window, "blur", this._fS);
			//阻止默认动作
			oEvent.preventDefault();
		};
		//附加程序
		this.onStart();
	},
	//修正范围
	Repair: function() {
		if (this.Limit) {
			//修正错误范围参数
			this.mxRight = Math.max(this.mxRight, this.mxLeft + this.Drag.offsetWidth);
			this.mxBottom = Math.max(this.mxBottom, this.mxTop + this.Drag.offsetHeight);
			//如果有容器必须设置position为relative或absolute来相对或绝对定位，并在获取offset之前设置
			!this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || CurrentStyle(this._mxContainer).position == "absolute" || (this._mxContainer.style.position = "relative");
		}
	},
	//拖动
	Move: function(oEvent) {
		//判断是否锁定
		if (this.Lock) {
			this.Stop();
			return;
		};
		//清除选择
		window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
		//设置移动参数
		var iLeft = oEvent.clientX - this._x,
			iTop = oEvent.clientY - this._y;
		//设置范围限制
		if (this.Limit) {
			//设置范围参数
			var mxLeft = this.mxLeft,
				mxRight = this.mxRight,
				mxTop = this.mxTop,
				mxBottom = this.mxBottom;
			//如果设置了容器，再修正范围参数
			if (!!this._mxContainer) {
				mxLeft = Math.max(mxLeft, 0);
				mxTop = Math.max(mxTop, 0);
				mxRight = Math.min(mxRight, this._mxContainer.clientWidth);
				mxBottom = Math.min(mxBottom, this._mxContainer.clientHeight);
			};
			//修正移动参数
			iLeft = Math.max(Math.min(iLeft, mxRight - this.Drag.offsetWidth), mxLeft);
			iTop = Math.max(Math.min(iTop, mxBottom - this.Drag.offsetHeight), mxTop);
		}
		//设置位置，并修正margin
		if (!this.LockX) {
			this.Drag.style.left = iLeft - this._marginLeft + "px";
		}
		if (!this.LockY) {
			this.Drag.style.top = iTop - this._marginTop + "px";
		}
		//附加程序
		this.onMove();
	},
	//停止拖动
	Stop: function() {
		//移除事件
		removeEventHandler(document, "mousemove", this._fM);
		removeEventHandler(document, "mouseup", this._fS);
		if (isIE) {
			removeEventHandler(this._Handle, "losecapture", this._fS);
			this._Handle.releaseCapture();
		} else {
			removeEventHandler(window, "blur", this._fS);
		};
		//附加程序
		this.onStop();
	}
};

export default Drag;
